20 March 2009

Optical illusions

You may have seen the recent “Give Motorcyclists a Second Thought” TV advertising campaign, commissioned by Transport for London. The ad uses an optical illusion which uses footage of vans, cars and motorcycles approaching at identical speeds. Drivers typically believe the larger vehicles will reach them quicker than the smaller motorcycles.

Psychologists call this the “size arrival effect” which has been demonstrated in a number of different studies. It also draws on the Italian psychologist Ponzo’s work back in 1913. Two same length lines are drawn between a pair of converging lines resembling railroad tracks going off into the distance. The upper line appears much larger because it spans a greater apparent distance between the rails which our minds assume are parallel. Ponzo suggested that our brains judge an object’s size based on its background.

The world we live in of course is 3D, but our eyes provide flat images. The ad says our brains make up the complete story and sometimes we get it wrong.

A recent study at the Ritsumeikan University in Kyoto showed that when people view illusions, it is not their imagination as we previously thought which makes them perceive movement, but part of the brain from the visual cortex, particularly the part related to physical movement detection which became active during the experiment. This finding may help designers to create better products that don’t confuse people through over elaborate design – particularly important in items such as surgical equipment, extreme sport kit and vehicles I would suggest!

For a good overview of optical illusions go to Wikepedia here http://en.wikipedia.org/wiki/Optical_illusion

I am interested in any input you have around optical illusions and tricking our brains.

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